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Math Help - Dice probability question

  1. #1
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    Dice probability question

    I am stuck on this...

    Q: If you roll 3 dice, what is the probability that the product of the 3 numbers will be a prime number (1,3,5,7,11,17) ?

    Thanks for the help!
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  2. #2
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    Make a Lattice or Tree diagram and count the results that give a prime.
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  3. #3
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    I got 5/108 ... does that sound right?
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  4. #4
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    Quote Originally Posted by Fiah View Post
    I got 5/108 ... does that sound right?
    Are there no more that 5 combinations whose product gives a prime number ....? By the way, 1 is not a prime number ... And your list is missing a prime number .... Perhaps your first step should be to review prime numbers.
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  5. #5
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    In this context, I considered '1' as a prime, I know it is not a true prime number. I did forget to put 2 in my prime number list, my mistake..


    ...(4/6)(1/6)(1/6) + (1/6)(3/6)(1/6)+ (1/6)(1/6)(3/6)
    ...4/216 + 3/216 + 3/216
    ...10/216 (reduce)
    ...5/108

    That's how I got 5/108
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